In a data center (Data Center), a rack unit (Rack Unit, or Rack for short) may accommodate multiple servers. Each server may be configured to manage one or more virtual machines VM (Virtual Machine). A server in the rack unit is connected to a Top of Rack (Top-of-Rack, ToR) switch. The Top of Rack switch (ToR Switch) is connected to another Top of Rack switch by using a Spine switch (Spine Switch) or a Spine switch fabric (Spine Fabric). In the data center, a network including a Top of Rack switch and a Spine switch is used to implement data communication between devices (physical machines and/or virtual machines) that are located in different rack units.
With rapid development in applications of cloud computing and big data, a data center network has become a research hotspot of various parties in academia and in industry in recent years. As a data center scale keeps increasing, requirements on the data center network are becoming more.
The first conventional technology is a relatively common two-tier Spine-Leaf fabric, and the fabric includes two-tier Spine-Leaf switches, where a Leaf switch is generally disposed on a top of a server rack, is used as an access switch of the server rack, and is also referred to as a Top-of-Rack (Top-of-Rack, ToR) switch, and a Spine switch is used as an aggregation (Aggregation) switch. A Spine switch and a Leaf switch that are included in this type of fabric are connected by using a Clos network (that is, each Spine switch at a Spine switch tier is connected to each Leaf switch at a Leaf switch tier). If a two-tier Spine-Leaf plane fabric is used, a data center scale depends on a quantity of downlink ports on a Spine switch. Therefore, the fabric is not applicable to construction of a large-scale or an ultra-large-scale data center.
Based on the above, the second conventional technology is a three-tier Core-Spine-Leaf plane fabric, which includes the two-tier Spine-Leaf fabric and a Core tier that is newly added on a basis of the two-tier Spine-Leaf fabric. A Spine switch and a Leaf switch are connected by using a Clos network, to form a network unit, and a Core switch tier and a Spine switch inside each network unit are also connected by using a Clos network. By means of forwarding by the Core switch tier, it can be implemented that multiple network units form a larger-scale network. If the second conventional technology is used, a problem about expansion of the data center scale is resolved to some extent; however, for construction of the data center network, in the fabric, a Core tier needs to be deployed outside a network unit, which increases network complexity and increases costs of network management and maintenance.